C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Engine Running Rich?

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Old Jan 6, 2018 | 04:07 PM
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Default Engine Running Rich?

When my 93 Corvette idles white smoke come out of the exhaust .Also the exhaust fumes are strong.Does this mean the engine is running rich?I do not get any codes.Just replaced spark plugs.What do I check next?
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Old Jan 6, 2018 | 04:16 PM
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White smoke is steam. Or more accurately, it was steam and it's condensed into vapor that you can see. Anyway, it's either b/c your car is cold and the air is cold (combustion makes steam/water)...or you're getting coolant into your combustion chamber(s)...likely a blown head gasket. Are you losing coolant?

Rich mixture causes black smoke. You need to get/find/borrow a scan tool and have someone look at your O2 sensor performance. You may simply need new O2 sensor(s).


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Last edited by Tom400CFI; Jan 6, 2018 at 04:21 PM.
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Old Jan 6, 2018 | 05:00 PM
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Originally Posted by Tom400CFI
White smoke is steam. Or more accurately, it was steam and it's condensed into vapor that you can see. Anyway, it's either b/c your car is cold and the air is cold (combustion makes steam/water)...or you're getting coolant into your combustion chamber(s)...likely a blown head gasket. Are you losing coolant?

Rich mixture causes black smoke. You need to get/find/borrow a scan tool and have someone look at your O2 sensor performance. You may simply need new O2 sensor(s).


.
When an O2 sensor is bad,i thought it would throw me a code saying the engine is running rich because of a bad O2 sensor.
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Old Jan 6, 2018 | 05:24 PM
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Sometimes they do.


Sometimes they don't.

Depends on if the O2's signal strays outside the realm of the ECM's acceptable criteria or not.
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Old Jan 7, 2018 | 09:39 PM
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Originally Posted by Tom400CFI
White smoke is steam. Or more accurately, it was steam and it's condensed into vapor that you can see. Anyway, it's either b/c your car is cold and the air is cold (combustion makes steam/water)...or you're getting coolant into your combustion chamber(s)...likely a blown head gasket. Are you losing coolant?

Rich mixture causes black smoke. You need to get/find/borrow a scan tool and have someone look at your O2 sensor performance. You may simply need new O2 sensor(s).
As far as the O2s if the ECM does not like the voltage swings it will stay in open loop. The car will run fine in open loop and not smoke if all is working correctly. Every time you drive the car it is in open loop till it warms up to temperature and you don’t know it and it will not smoke. It's just that the mileage will be bad cause it's slightly on the rich side.

As said, get a scan tool for OBD1 and look at the fuel trim numbers.
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